Classification and structure-activity relationships of fluoroquinolones

Efflux Pump (QacA, QacB, and QacC) and β-Lactamase Inhibitors? An Evaluation of 1,8-Naphthyridines against Staphylococcus aureus Strains

The bacterial species Staphylococcus aureus presents a variety of resistance mechanisms, among which the expression of β-lactamases and efflux pumps stand out for providing a significant degree of resistance to clinically relevant antibiotics. The 1,8-naphthyridines are nitrogen heterocycles with a broad spectrum of biological activities and, as such, are promising research targets. However, the potential roles of these compounds on bacterial resistance management remain to be better investigated. Therefore, the present study evaluated the antibacterial activity of 1,8-naphthyridine sulfonamides, addressing their ability to act as inhibitors of β-lactamases and efflux pump (QacA/B and QacC) against the strains SA-K4414 and SA-K4100 of S. aureus. All substances were prepared at an initial concentration of 1024 μg/mL, and their minimum inhibitory concentrations (MIC) were determined by the broth microdilution method. Subsequently, their effects on β-lactamase- and efflux pump-mediated antibiotic resistance was evaluated from the reduction of the MIC of ethidium bromide (EtBr) and β-lactam antibiotics, respectively. The 1,8-naphthyridines did not present direct antibacterial activity against the strains SA-K4414 and SA-K4100 of S. aureus. On the other hand, when associated with antibiotics against both strains, the compounds reduced the MIC of EtBr and β-lactam antibiotics, suggesting that they may act by inhibiting β-lactamases and efflux pumps such as QacC and QacA/B. However, further research is required to elucidate the molecular mechanisms underlying these observed effects.

Ab initio molecular dynamics simulations and experimental speciation study of levofloxacin under different pH conditions

Levofloxacin is an extensively employed broad-spectrum antibiotic belonging to the fluoroquinolone class. Despite the extremely wide usage of levofloxacin for a plethora of diseases, the molecular characterization of this antibiotic appears quite poor in the literature. Moreover, the acid-base properties of levofloxacin - crucial for the design of efficient removal techniques from wastewaters - have never extensively been investigated so far. Here we report on a study on the behavior of levofloxacin under standard and diverse pH conditions in liquid water by synergistically employing static quantum-mechanical calculations along with experimental speciation studies. Furthermore, with the aim of characterizing the dynamics of the water solvation shells as well as the protonation and deprotonation mechanisms, here we present the unprecedented quantum-based simulation of levofloxacin in aqueous environments by means of state-of-the-art density-functional-theory-based molecular dynamics. This way, we prove the cooperative role played by the aqueous hydration shells in assisting the proton transfer events and, more importantly, the key place held by the nitrogen atom binding the methyl group of levofloxacin in accepting excess protons eventually present in water. Finally, we also quantify the energetic contribution associated with the presence of a H-bond internal to levofloxacin which, on the one hand, stabilizes the ground-state molecular structure of this antibiotic and, on the other, hinders the first deprotonation step of this fluoroquinolone. Among other things, the synergistic employment of quantum-based calculations and speciation experiments reported here paves the way toward the development of targeted removal approaches of drugs from wastewaters.

Fluoroquinolones: Blessings Or Curses

Fluoroquinolones are one of the world's most valuable and popularly used categories of antimicrobial agents. This paper attempts to review the substantial progress of fluoroquinolones from their discovery to black box warning. Antibiotic drug choice will remain difficult in the presence of increasing resistance, but the introduction of fluoroquinolones has created a new and exciting era in antimicrobial treatment. These are a synthetic heterogeneous group of compounds used in both hospital and community practices to treat numerous severe infections. The era of quinolone antibiotics began with the serendipitous discovery of the quinolone prototype in 1962. The chronological development of fluoroquinolone reported that nalidixic acid was the first quinolone that gained popular choice for the treatment of urinary tract infection. The subsequent agents like levofloxacin, ofloxacin, norfloxacin, gatifloxacin, moxifloxacin, clinafloxacin, sparfloxacin, and ciprofloxacin were derived through side chain and nuclear manipulation from basic pharmacophore. The fluoroquinolone motifs have been found as a milestone, effective in certain infections that are respiratory tract infection, urinary tract infection, bone disorders, meningococcal and mycobacterial infections, sexually transmitted diseases, skin infections, etc. Fluoroquinolones are first entirely man-made antibiotics that exhibit antibacterial activity through the inhibition of topoisomerase II, topoisomerase IV and deoxyribonucleic acid gyrase, which is vital for chromosome replication and function. The post-marketing surveillance pointed out the favorable side effects associated with fluoroquinolones such as phototoxicity, QT interval prolongation and anaphylaxis. The discovery, development and clinical use of fluoroquinolone antibiotics in the last century contributed to a decline in morbidity and mortality rates.

Carbon-based adsorbents for fluoroquinolone removal from water and wastewater: A critical review

This review summarizes the adsorptive removal of Fluoroquinolones (FQ) from water and wastewater. The influence of different physicochemical parameters on the adsorptive removal of FQ-based compounds is detailed. Further, the mechanisms involved in the adsorption of FQ-based antibiotics on various adsorbents are succinctly described. As the first of its kind, this paper emphasizes the performance of each adsorbent for FQ-type antibiotic removal based on partition coefficients of the adsorbents that is a more sensitive parameter than adsorption capacity for comparing the performances of adsorbents under various adsorbate concentrations and heterogeneous environmental conditions. It was found that π-π electron donor-acceptor interactions, electrostatic interactions, and pore-filling were the most prominent mechanisms for FQ adsorption by carbon and clay-based adsorbents. Among all the categories of adsorbents reviewed, graphene showed the highest performance for the removal of FQ antibiotics from water and wastewater. Based on the current state of knowledge, this review fills the gap through methodolically understanding the mechanism for further improvement of FQ antibiotics adsorption performance from water and wastewater.

Chemical synthesis, molecular docking and MepA efflux pump inhibitory effect by 1,8-naphthyridines sulfonamides

This study aimed to evaluate the antibacterial activity and to verify, in silico and in vitro, the inhibition of efflux mechanisms using a series of synthesized 1,8-naphthyridines sulfonamides against Staphylococcus aureus strains carrying MepA efflux pumps. The chemical synthesis occurred through the thermolysis of the Meldrum's acid adduct. The sulfonamide derivatives were obtained by the sulfonylation of 2-amino-5‑chloro-1,8-naphthyridine with commercial benzenesulfonyl chloride. Antibacterial activity was assessed by the broth microdilution test. Efflux pump inhibitory capacity was evaluated in silico by molecular docking and in vitro by analyzing synergistic effects on ciprofloxacin and ethidium bromide (EtBr) and by EtBr fluorescence emission assays. The following 1,8-naphthyridines were synthesized: 4-methyl-N-(5‑chloro-1,8-naphthyridin-2-yl)-benzenesulfonamide (Compound 10a); 2,5-dichloro-N-(5‑chloro-1,8-naphthyridin-2-yl)-benzenesulfonamide (Compound 10b); 4-fluoro-N-(5‑chloro-1,8-naphthyridin-2-yl)-benzenesulfonamide (Compound 10c); 2,3,4-trifluoro-N-(5‑chloro-1,8-naphthyridin-2-yl)-benzenesulfonamide (Compound 10d); 3-trifluoromethyl-N-(5‑chloro-1,8-naphthyridin-2-yl)-benzenesulfonamide (Compound 10e); 4‑bromo-2,5-difluoro-N-(5‑chloro-1,8-naphthyridin-2-yl)-benzenesulfonamide (Compound 10f). The 1,8-naphthyridines derivatives associated with sulfonamides did not show antibacterial activity. However, they showed a favorable pharmacokinetic profile with possible MepA efflux pump inhibitory action, demonstrated in molecular docking. In addition to the promising results in reducing the concentration of intracellular EtBr. 1,8-naphthyridines act as putative agents in the inhibitory action of the MepA efflux pump.

Evaluation of Pipemidic Acid Derivatives for Potential Antimicrobial Activity Application: In silico Studies on Bioactivity

Background:

Pipemidic acid is a broad-spectrum quinolone antibacterial agent for the treatment of chronic urinary tract infections against both gram-positive and gram-negative bacteria. Both quinolone and fluoroquinolone antibiotics have been useful in combating bacterial infections. However, patients suffer severe side effects when they stop taking the medication. The piperazinyl region of pipemidic acid is highly responsible for the side effects.

Objective:

The objective of this study is to design new compounds in which the piperazinyl region is masked by way of conjugation to benzoic acid derivatives.

Methods:

In silico studies were conducted using AutoDockTools software for ligand-protein docking. The docking scores were compared to the parent pipemidic acid docked to Bacterial DNA (deoxyribonucleic acid) gyrase and GABA (gamma-Aminobutyric acid) receptor from the PDB (Protein Data Bank) database. Sites of metabolism, biological activity, quantum chemical descriptors, and ADME (absorption, distribution, metabolism, and excretion) property predictions for each designed ligand were also evaluated.

Results:

The docking studies and biological activity predictions showed good anti-infective properties (ligand PAR03) whilst also suggesting a reduction in GABA receptor agonist activity. The performance of PAR03 correlates with its electronic properties showing electrophilic character (can generate Reactive Electrophilic Species (RES)).

Conclusion:

The results from this study indicate that modification of the piperazinyl region of pipemidic acid can be an effective way to improve the drug potency whilst also ensuring reduction of the associated side effects.

Photosensitivity induced by lomefloxacin versus other fluoroquinolones: A meta-analysis

Lomefloxacin may be more likely than other fluoroquinolones to cause photosensitivity. However, the rate of photosensitivity is variable and a meta-analysis has yet to be performed. The aim of this meta-analysis is to compare the rate of photosensitivity between outpatients who received lomefloxacin and those who received other fluoroquinolones. PubMed, EMBASE, Cochrane Library databases and trial registries were searched for randomized controlled trials (RCTs) of outpatients through June 12, 2019. The study outcome was the rate of photosensitivity based on the intention-to-treat principle, estimated by risk difference (RD) as the primary analysis and Peto odds ratio (Peto OR) as the secondary analysis, with 95% confidence intervals (CIs) using random-effects models. Four RCTs (total of 2295 patients) were included in this meta-analysis. A statistically higher risk of photosensitivity was found with lomefloxacin than with other fluoroquinolones (RD, 3.4%; 95% CI, 0.7%-6.2%; P-value = 0.013; I² = 10.9%). The odds of photosensitivity was also significantly higher with lomefloxacin (Peto OR, 5.81; 95% CI, 3.34 to 10.11; P-value <0.001; I² = 0%). This meta-analysis of RCTs found significantly higher photosensitivity with lomefloxacin compared to other fluoroquinolones. Considering this finding and given its lack of additional efficacy compared to other fluoroquinolones, lomefloxacin as a fluoroquinolone option should potentially be reconsidered.

The effects of Mannheimia haemolytica and albendazole on marbofloxacin pharmacokinetics in lambs

The study aimed to define the effects of M. haemolytica and a single oral dose of albendazole on the single-dose pharmacokinetics of marbofloxacin in lambs. The pharmacokinetic-pharmacodynamic integration of marbofloxacin was applied to describe a 3 mg/kg intramuscular dose in lambs. The 6 healthy and 12 naturally infected with M. haemolytica lambs (Akkaraman, males weighing 10-15 kg and aged 2-3 months) were used in this study. In the marbofloxacin group, 6 healthy lambs received marbofloxacin. In the albendazole group after 2 weeks washout period, the same animals received marbofloxacin on 1 h after albendazole. In the diseased marbofloxacin group, 6 lambs naturally infected with M. haemolytica received marbofloxacin. In the diseased albendazole group, 6 lambs naturally infected with M. haemolytica received marbofloxacin on 1 h after albendazole. The marbofloxacin and albendazole were administered each as a single dose of 3 mg/kg intramuscular and 7.5 mg/kg oral, respectively, in the respective groups. Plasma concentration of marbofloxacin was measured with HPLC-UV and pharmacokinetic parameters were analyzed by non-compartmental model. Albendazole did not change the pharmacokinetic profiles of marbofloxacin in healthy and diseased lambs. However, M. haemolytica affected the pharmacokinetics of marbofloxacin in diseased lambs, AUC_0-24/MIC₉₀ ratio was not found to be higher than 125, but C_max/MIC₉₀ ratios was found to be higher than 10 for an MIC value of 0.25 μg/mL in all groups. The marbofloxacin dose described in this study may not be effective for the treatment of infections due to M. haemolytica in lambs, with MIC ≤ 0.25 μg/mL.

Fluoroquinolones (FQs) in the environment: A review on their abundance, sorption and toxicity in soil

The use of fluoroquinolones (FQs) antibiotics as therapeutic agents and growth promoters is increasing worldwide; however their extensive uses are also resulting in antibiotic resistance among world communities. FQs have also become one of the major contaminants in the waste water bodies, which are not even completely removed during the treatment processes. Furthermore, their abundance in agricultural resources, such as the irrigation water, the bio-solids and the livestock manure can also affect the soil micro-environment. These antibiotics in soil tend to interact in several different ways to affect soil flora and fauna. The current review endeavors to highlight the some critical aspects of FQs prevalence in the environment. The review presents a detailed discussion on the pathways and abundance of FQs in soil. The discussion further spans the issue of sorption and FQs transformation into the soil better understand of their behavior and their toxicity to soil flora and fauna.

Fluoroquinolone-Related Neuropsychiatric Events in Hospitalized Veterans

OBJECTIVE

To measure the incidence and risk factors for fluoroquinolone (ciprofloxacin, moxifloxacin, and levofloxacin)-associated psychosis or delirium in a veteran population.

METHODS

A retrospective study was conducted in the Western New York Veterans Affairs Health System (2005-2013). Participants were hospitalized veterans receiving a fluoroquinolone for at least 48 hours (n = 631). Cases of delirium or psychosis were defined by the Diagnostic and Statistical Manual of Mental Disorders-IV criteria, and the Naranjo scale (score ≥ 1) was used to determine the probability of the adverse drug reaction being related to fluoroquinolones. A bivariate analysis of covariates followed by a multivariate logistic regression was used to determine predisposing factors to the development of delirium/psychosis.

RESULTS

The mean age of the population was 71.5 years (range: 22-95). Fluoroquinolone-associated delirium/psychosis occurred in 3.7% of the inpatients studied (n = 23). The median Naranjo score was 3 indicating a possible association. Psychosis/delirium occurred in 3.6% of ciprofloxacin-treated patients (n = 14/391), 4.5% of patients-treated with moxifloxacin (n = 9/200), and 0% of those receiving levofloxacin (n = 0/40); p = 0.4. Significant risk factors for development of delirium/psychosis in patients receiving a fluoroquinolone in the multivariate logistical regression included typical antipsychotic use (OR, 5.4; 95% CI: 1.4-16.7) and age. A 10-year increase in age was associated with a 1.8-fold greater odds of a neuropsychiatric event.

CONCLUSIONS

Fluoroquinolones may be more commonly associated with delirium/psychosis than originally reported in this veteran population. Caution should be used when prescribing a fluoroquinolone for patients on typical antipsychotics and those of advanced age.

A Review of New Fluoroquinolones : Focus on their Use in Respiratory Tract Infections

The new respiratory fluoroquinolones (gatifloxacin, gemifloxacin, levofloxacin, moxifloxacin, and on the horizon, garenoxacin) offer many improved qualities over older agents such as ciprofloxacin. These include retaining excellent activity against Gram-negative bacilli, with improved Gram-positive activity (including Streptococcus pneumoniae and Staphylococcus aureus). In addition, gatifloxacin, moxifloxacin and garenoxacin all demonstrate increased anaerobic activity (including activity against Bacteroides fragilis). The new fluoroquinolones possess greater bioavailability and longer serum half-lives compared with ciprofloxacin. The new fluoroquinolones allow for once-daily administration, which may improve patient adherence. The high bioavailability allows for rapid step down from intravenous administration to oral therapy, minimizing unnecessary hospitalization, which may decrease costs and improve quality of life of patients. Clinical trials involving the treatment of community-acquired respiratory infections (acute exacerbations of chronic bronchitis, acute sinusitis, and community-acquired pneumonia) demonstrate high bacterial eradication rates and clinical cure rates. In the treatment of community-acquired respiratory tract infections, the various new fluoroquinolones appear to be comparable to each other, but may be more effective than macrolide or cephalosporin-based regimens. However, additional data are required before it can be emphatically stated that the new fluoroquinolones as a class are responsible for better outcomes than comparators in community-acquired respiratory infections. Gemifloxacin (except for higher rates of hypersensitivity), levofloxacin, and moxifloxacin have relatively mild adverse effects that are more or less comparable to ciprofloxacin. In our opinion, gatifloxacin should not be used, due to glucose alterations which may be serious. Although all new fluoroquinolones react with metal ion-containing drugs (antacids), other drug interactions are relatively mild compared with ciprofloxacin. The new fluoroquinolones gatifloxacin, gemifloxacin, levofloxacin, and moxifloxacin have much to offer in terms of bacterial eradication, including activity against resistant respiratory pathogens such as penicillin-resistant, macrolide-resistant, and multidrug-resistant S. pneumoniae. However, ciprofloxacin-resistant organisms, including ciprofloxacin-resistant S. pneumoniae, are becoming more prevalent, thus prudent use must be exercised when prescribing these valuable agents.

Acute symptomatic seizures and systemic illness

PURPOSE OF REVIEW

This article addresses the occurrence of acute symptomatic seizures in the setting of many medical illnesses.

RECENT FINDINGS

Many medical illnesses can cause seizures. Metabolic derangements, such as disorders of serum glucose metabolism, cause seizures, as well as other neurologic manifestations. Many medicines (such as antibiotics, antivirals, antidepressants, and antipsychotics), whether used at typical doses or in overdosage, can lead to acute symptomatic seizures.

SUMMARY

Acute symptomatic seizures occur most often in illnesses that directly injure the brain. Trauma, stroke, CNS tumors, and CNS infection very commonly cause seizures. However, many medical illnesses do not directly injure the brain but lead to neurologic signs and symptoms, such as seizures. Recognizing these effects, especially in critically ill patients, is important for optimizing medical care.

Synthesis and in vitro antibacterial activity of a series of novel gatifloxacin derivatives

A series of novel gatifloxacin (GTFX) derivatives were designed, synthesized and characterized by (1)H NMR, (13)C NMR, MS and HRMS. These derivatives were evaluated for in vitro antibacterial activity against representative Gram-positive and Gram-negative strains. Our results reveal that most of the target compounds show good potency in inhibiting the growth of Staphylococcus aureus including MRSA and Staphylococcus epidermidis including MRSE. Compounds 8, 14 and 20 have useful activity against all of the tested Gram-positive and Gram-negative strains (MICs: 0.06-4 μg/mL). In particular, 20 possessing a broad antimicrobial spectrum (MICs: 0.06-1 μg/mL) was found to be 2-32-folds more potent than the reference drug levofloxacin and parent GTFX against Pseudomonas aeruginosa.

Synthesis and in vitro antibacterial activity of 7-(3-alkoxyimino-5-amino/methylaminopiperidin-1-yl)fluoroquinolone derivatives

We report herein the design and synthesis of novel 7-(3-alkoxyimino-5-amino/methylaminopiperidin-1-yl)fluoroquinolone derivatives based on the structures of new fluoroquinolones IMB and DZH. The antibacterial activity of these newly synthesized compounds was also evaluated and compared with gemifloxacin, ciprofloxacin, and levofloxacin. Results revealed that all of the target compounds 10-27 have good potency in inhibiting the growth of Staphylococcus aureus including MSSA (MIC: 0.125-8 μg/mL), Staphylococcus epidermidis including MRSE (MIC: 0.25-16 μg/mL), Streptococcus pneumoniae (MIC: 0.125-4 μg/mL), and Escherichia coli (MIC: 0.25-0.5 μg/mL). In particular, some compounds showed useful activity against several fluoroquinolone-resistant strains, and the most active compound 15 was found to be 16-128, 2-32, and 4-8-fold more potent than the three reference drugs against fluoroquinolone-resistant MSSA, MRSA, and MRSE.

Safety profile of the fluoroquinolones: focus on levofloxacin

The fluoroquinolone class of antibacterial agents are among the most frequently prescribed drugs, with utility in a broad range of bacterial infections. Although very useful agents, the fluoroquinolones as a class are associated with a number of adverse events, some with considerable clinical significance. In the past 15-20 years, tolerability concerns have led to restrictions on the use of the fluoroquinolones and, in some instances, the withdrawal of agents from the market. This review focuses on the safety and tolerability of levofloxacin, a third-generation fluoroquinolone, relative to other fluoroquinolones. A literature search was performed of the MEDLINE database encompassing the dates 1980-2009, using as keywords the drug names levofloxacin and concurrently marketed fluoroquinolones combined with the words 'safety', 'adverse effect' or 'adverse drug reaction', or the name of the specific adverse effect. Adverse events commonly associated with the fluoroquinolones include gastrointestinal and CNS toxicity (most frequently headache and dizziness), as well as other adverse events including ECG abnormalities (for example QT interval prolongation), disrupted glucose metabolism, phototoxicity, tendon and joint disorders, hypersensitivity and skin disorders, and hepatic toxicity. Package inserts for the fluoroquinolones in Europe and the US contain warnings regarding these risks. US package inserts also carry 'black-box' warnings regarding the risk of tendon rupture and joint disorders with these agents; however, there is a substantial body of evidence to indicate that there are marked differences in the tolerability profiles of the individual agents within the fluoroquinolone class. These differences may be explained, at least in part, by structural differences: all fluoroquinolones share a basic quinolone core, with differences in specific side chains underlying the adverse event relationships. Furthermore, many of the fluoroquinolone-associated adverse effects and toxicities occur more frequently in patients with pre-existing risk factors, or in certain subpopulations. Notably, package inserts for the fluoroquinolones carry warnings regarding use in the elderly, paediatric patients and patients with pre-existing, or factors predisposing to, seizure disorders. Because of this, many adverse reactions with these agents could be prevented by improving patient screening and education. The recent withdrawal of gatifloxacin due to dysglycaemia makes it timely to review the safety and tolerability of the individual agents in this class. Overall, it appears that levofloxacin is relatively well tolerated, with low rates of clinically important adverse events such as CNS toxicity, cardiovascular toxicity and dysglycaemia.

Detection and prevention of ocular phototoxicity of ciprofloxacin and other fluoroquinolone antibiotics

Fluoroquinolone (FLQ) drugs are a potent family of antibiotics used to treat infections including ocular infections. To determine if these antibiotics may be phototoxic to the eye, we exposed human lens epithelial cells to 0.125-1 mm FLQs (ciprofloxacin [Cipro], lomefloxacin [Lome], norfloxacin [Nor] and ofloxacin [Ofl]), the precursor quinolone nalidixic acid (Nalid) and UVA radiation (2.5 J cm(-2)). Based on fluorescence confocal microscopy, FLQs are diffused throughout the cytoplasm and preferentially located in the lysosomes of lens epithelial cells. Neither FLQ exposure alone nor UVA exposure alone reduced cell viability. However, with exposure to UVA radiation the FLQs studied (Cipro, Nor, Lome and Ofl) induced a phototoxic reaction that included necrosis, apoptosis, loss of cell viability as measured by MTS, and membrane damage as determined by the lactate dehydrogenase assay. Both Nalid and all FLQs studied (Cipro, Nor, Lome and Ofl) photopolymerized the lens protein alpha-crystallin. Phototoxic damage to lens epithelial cells and/or alpha-crystallin will lead to a loss of transparency of the human lens. However, if precautions are taken to filter all UV radiation from the eye while taking these antibiotics, eye damage may be prevented.

Ocular toxicity of fluoroquinolones

The ocular toxicity of fluoroquinolones and the risks of their use in the treatment of ocular infection were reviewed. Systematic identification, selection, review and synthesis of published English-language studies relating to fluoroquinolone use and safety in animals and humans was conducted. Although not free of complications, fluoroquinolones are generally safe when used to treat ocular infection. Ocular toxicity appears to be dose-dependent and results from class-effects and specific fluoroquinolone structures. Phototoxicity and neurotoxicity have been reported, and toxic effects on ocular collagen may be associated with Achilles tendinopathy. Corneal precipitation may provide an advantageous drug depot but delay healing and result in corneal perforation in approximately 10% of cases. Although human toxicity studies are limited, the current recommended dose for intracameral injection of ciprofloxacin is less than 25 microg. Intravitreal injections of ciprofloxacin 100 microg, ofloxacin 50 microg/mL, trovafloxacin 25 microg or less, moxifloxacin 160 microg/0.1 mL or less and pefloxacin 200 microg/0.1 mL are considered safe.

Synthesis and antibacterial activity of novel fluoroquinolones containing substituted piperidines

The design and synthesis of new fluoroquinolone antibacterial agents having substituted piperidine rings at the C-7 position are described. Most of the new compounds demonstrated high in vitro antibacterial activity. Several of them exhibited significant activities against gram-positive organisms, which were more potent than those of gemifloxacin, Linezolid, and vancomycin.

Determination of fluorinated quinolone antibacterials by ion chromatography with fluorescence detection

For preparing fluorinated quinolone antibiotic medicine locally used in stomatology, simultaneous determination of norfloxacin, ciprofloxacin, and enoxacin was carried out by multiphase ion chromatography with fluorescence detection. Quinolone antibiotics were separated by Dionex OmniPac PAX-500 column with an eluent of 15 mmol/L H(2)SO(4) and 35% methanol (v/v) at a flow-rate of 1.0 ml/min and detected with fluorescence with excitation and emission wave lengths of 347 nm and 420 nm respectively. The detection limits (S/N=3) of norfloxacin, ciprofloxacin and enoxacin were 50, 105 and 80 ng/ml respectively. The relative standard deviations of retention time, peak area and peak height were less than 1.1% and good linear relationship resulted. The developed method was applied to pharmaceutical formulations and biological fluids.

Levofloxacin for the treatment of community-acquired pneumonia

New respiratory fluoroquinolones (FQs), such as levofloxacin, offer many improved qualities over older agents, such as ciprofloxacin. These include retaining excellent Gram-negative bacilli activity, with improved Gram-positive activity. New FQ-like levofloxacin possesses greater bioavailabilty and a longer serum half-life compared with ciprofloxacin, allowing for once-daily dosing, which may improve patient adherence. The high bioavailability of levofloxacin allows for rapid step-down from intravenous administration to oral therapy, minimizing unnecessary hospitalization, which may decrease costs and improve patient quality of life. Levofloxacin has been evaluated for the treatment of community-acquired pneumonia (CAP) in numerous randomized clinical trials. Most published studies have used the 500 mg dose, although more recent studies have investigated the 750 mg dose once daily. These trials demonstrate that levofloxacin is effective and safe for the treatment of CAP, displaying relatively mild adverse effects that are more or less comparable with ciprofloxacin. Levofloxacin has much to offer in terms of bacterial eradication, including for resistant respiratory pathogens. However, ciprofloxacin-resistant organisms are becoming more prevalent so prudence must be exercised when prescribing this agent.

Fluoroquinolone antibiotics in the environment

Fluoroquinolones (FQs) are used in large amounts for human and animal medical care. They are excreted as parent compound, as conjugates, or as oxidation, hydroxylation, dealkylation, or decarboxylation products of the parent compound. A considerable amount of FQs and their metabolites may reach the soil as constituents of urine, feces, or manure. The residues of FQs in foods of animal origin may pose hazards to consumers through emergence of drug-resistant bacteria. FQs bind strongly to topsoil, reducing the threat of surface water and groundwater contamination. The strong binding of FQs to soil and sediments delays their biodegradation and explains the recalcitrance of FQs. Wastewater treatment is an efficient elimination step (79%-87% removal) for FQs before they enter rivers. FQs are susceptible to photodegradation in aqueous medium, involving oxidation, dealkylation, and cleavage of the piperazine ring.

Prulifloxacin: a new antibacterial fluoroquinolone

In the last few years, the antimicrobial activity, efficacy and relative safety of fluoroquinolones have made them attractive for the treatment of community-acquired and nosocomial infections. Prulifloxacin is a new fluoroquinolone antibacterial agent with a broad spectrum of activity against Gram-positive and -negative bacteria. Prulifloxacin is available for oral use, and after absorption is metabolized in to the active form, ulifloxacin. It exhibits good penetration in target tissues and a long elimination half-life, allowing once-daily administration. A number of randomized, controlled clinical trials carried out in Europe demonstrated the efficacy of prulifloxacin in the treatment of urinary tract (acute uncomplicated and complicated) and respiratory tract infections (acute exacerbations of chronic bronchitis), in comparison with the most widely used drugs such as ciprofloxacin, co-amoxiclav and pefloxacin. Prulifloxacin was generally well tolerated. The most frequent adverse reactions observed in clinical trials were gastric pain, diarrhea, nausea and skin rash. This review focuses on the characteristics of prulifloxacin, summarizing the relevant preclinical and clinical data.

Design, synthesis, and evaluation of novel 6-chloro-/fluorochromone derivatives as potential topoisomerase inhibitor anticancer agents

6-Chloro-2-pyrrolidino-/morpholino-/piperidino-/N-methylpiperazino-3-formyl-chromones (13-16) and 6-fluoro-2,7-di-morpholino-/piperidino-/N-methylpiperazino-3-formylchromones (17-19) have been synthesized as potential topoisomerase inhibitor anticancer agents, and evaluated, in vitro, against Ehrlich ascites carcinoma (EAC) cells, and also in vivo on EAC bearing mice. The compounds displayed promising anticancer activity under these test systems and shall serve as useful 'leads' for further design.

Crystallographic studies on two bioisosteric analogues, N-acetyl-beta-D-glucopyranosylamine and N-trifluoroacetyl-beta-D-glucopyranosylamine, potent inhibitors of muscle glycogen phosphorylase

Structure-based inhibitor design has led to the discovery of a number of potent inhibitors of glycogen phosphorylase b (GPb), N-acyl derivatives of beta-D-glucopyranosylamine, that bind at the catalytic site of the enzyme. The first good inhibitor in this class of compounds, N-acetyl-beta-D-glucopyranosylamine (NAG) (K(i) = 32 microM), has been previously characterized by biochemical, biological and crystallographic experiments at 2.3 angstroms resolution. Bioisosteric replacement of the acetyl group by trifluoroacetyl group resulted in an inhibitor, N-trifluoroacetyl-beta-D-glucopyranosylamine (NFAG), with a K(i) = 75 microM. To elucidate the structural basis of its reduced potency, we determined the ligand structure in complex with GPb at 1.8 angstroms resolution. To compare the binding mode of N-trifluoroacetyl derivative with that of the lead molecule, we also determined the structure of GPb-NAG complex at a higher resolution (1.9 angstroms). NFAG can be accommodated in the catalytic site of T-state GPb at approximately the same position as that of NAG and stabilize the T-state conformation of the 280 s loop by making several favourable contacts to Asn284 of this loop. The difference observed in the K(i) values of the two analogues can be interpreted in terms of subtle conformational changes of protein residues and shifts of water molecules in the vicinity of the catalytic site, variations in van der Waals interaction, and desolvation effects.

Quinolones in 2005: an update

Quinolones are one of the largest classes of antimicrobial agents used worldwide. This review considers the quinolones that are available currently and used widely in Europe (norfoxacin, ciprofloxacin, ofloxacin, levofloxacin and moxifloxacin) within their historical perspective, while trying to position them in the context of recent and possible future advances based on an understanding of: (1) their chemical structures and how these impact on activity and toxicity; (2) resistance mechanisms (mutations in target genes, efflux pumps); (3) their pharmacodynamic properties (AUC/MIC and Cmax/MIC ratios; mutant prevention concentration and mutant selection window); and (4) epidemiological considerations (risk of emergence of resistance, clonal spread). Their main indications are examined in relation to their advantages and drawbacks. Overall, it is concluded that these important agents should be used in an educated fashion, based on a careful balance between their ease of use and efficacy vs. the risk of emerging resistance and toxicity. However, there is now substantial evidence to support use of the most potent drug at the appropriate dose whenever this is required.

Symmetric fluoro-substituted diol-based HIV protease inhibitors. Ortho-fluorinated and meta-fluorinated P1/P1'-benzyloxy side groups significantly improve the antiviral activity and preserve binding efficacy

HIV-1 protease is a pivotal enzyme in the later stages of the viral life cycle which is responsible for the processing and maturation of the virus particle into an infectious virion. As such, HIV-1 protease has become an important target for the treatment of AIDS, and efficient drugs have been developed. However, negative side effects and fast emerging resistance to the current drugs have necessitated the development of novel chemical entities in order to exploit different pharmacokinetic properties as well as new interaction patterns. We have used X-ray crystallography to decipher the structure-activity relationship of fluoro-substitution as a strategy to improve the antiviral activity and the protease inhibition of C2-symmetric diol-based inhibitors. In total we present six protease-inhibitor complexes at 1.8-2.3 A resolution, which have been structurally characterized with respect to their antiviral and inhibitory activities, in order to evaluate the effects of different fluoro-substitutions. These C2-symmetric inhibitors comprise mono- and difluoro-substituted benzyloxy side groups in P1/P1' and indanoleamine side groups in P2/P2'. The ortho- and meta-fluorinated P1/P1'-benzyloxy side groups proved to have the most cytopathogenic effects compared with the nonsubstituted analog and related C2-symmetric diol-based inhibitors. The different fluoro-substitutions are well accommodated in the protease S1/S1' subsites, as observed by an increase in favorable Van der Waals contacts and surface area buried by the inhibitors. These data will be used in the development of potent inhibitors with different pharmacokinetic profiles towards resistant protease mutants.

Urinary bactericidal activity, urinary excretion and plasma concentrations of gatifloxacin (400 mg) versus ciprofloxacin (500 mg) in healthy volunteers after a single oral dose

In an open randomised double-crossover study 12 volunteers (six men, six women) received a single oral dose of gatifloxacin (400 mg) or ciprofloxacin (500 mg) to assess urinary bactericidal activity (in eight intervals up to 120 h) and pharmacokinetic (PK) parameters (up to 36 h). Plasma concentrations and urinary excretion were determined by HPLC with fluorescence detection, and urinary bactericidal titers (UBT) by microdilution-method, using antibiotic-free urine of each volunteer. The mean maximum plasma concentration of gatifloxacin was 3.35 mg/l and that of ciprofloxacin 2.12 mg/l. The mean (median) cumulative renal excretion of the parent drug was for gatifloxacin 81 (83)% of the administered dose within 120 h and for ciprofloxacin 43 (45)%. The UBTs, i.e. the highest two-fold dilution (antibiotic-free urine as diluent) of urine still being bactericidal, were determined for an Escherichia coli ATCC reference strain and nine clinical uropathogens with the following MICs (mg/l) for gatifloxacin/ciprofloxacin (microdilution, MHB): E. coli ATCC 25922 (0.008/0.008); E. coli 523 (0.06/0.06); Klebsiella pneumoniae 1058 (0.03/0.016); Proteus mirabilis 524 (0.125/0.016); Pseudomonas aeruginosa 561 (1/0.125); Enterococcus faecalis strains 60 an 55 (0.5/1 and 8/32); Staphylococcus aureus strains 248 and 596 (both 0.03/0.125) and S. saprophyticus Ho94 (0.125/0.25). The median UBTs measured within the first 6h for gatifloxacin were between 1:16 and 1:>or=1024 for the Gram-negative strains including P. aeruginosa and between 1:8 and 1:>or=1024 for the five Gram-positive strains. The median UBTs for ciprofloxacin were between 1:64 and 1:>or=1024 for the Gram-negative strains (incl P. aeruginosa) and between 1:1.5 and 1:768 for the five Gram-positive strains. The UBTs up to 12 < 0.05 h showed no difference (P<0.05 ) for both E. coli strains, but ciprofloxacin was superior to gatifloxacin against Klebsiella, Proteus and Pseudomonas strains and gatifloxacin was superior to ciprofloxacin against all Gram-positive strains. For the UBTs at 12-24 h, gatifloxacin was generally superior to ciprofloxacin, but showed no difference in the Proteus and Pseudomonas strains. The areas under the UBT-time-curve (AUBT) up to 120 h showed statistically significant (P ) differences between both quinolones in favour of gatifloxacin against 8 of 10 strains tested, no difference for P. mirabilis and significantly higher activity of ciprofloxacin against P. aeruginosa. In conclusion, gatifloxacin and ciprofloxacin had overall comparable initial urinary bactericidal activity with some differences for specific pathogens, some times in favour of gatifloxacin (Gram-positives) and some times of ciprofloxacin (usually Gram-negatives), suggesting that for empiric therapy a single oral dose of gatifloxacin (400mg) would be clinically equivalent to ciprofloxacin (500 mg) twice daily-in agreement with the results of a clinical study in complicated UTI performed previously [Int. J. Antimicrob. Agents (2004)].

Chemometric Studies on the Bactericidal Activity of Quinolones via an Extended VolSurf Approach

An extended VolSurf approach, that additionally includes SHAPE descriptors, was applied to a dataset of 55 quinolones. Bactericidal activity was measured at Bayer AG, Germany, for Gram-negative (Escherichia coli and Pseudomonas aeruginosa) and Gram-positive bacteria (Staphylococcus aureus and Enterococcus faecalis). Chemometric analysis was first approached via a classical VolSurf approach. The following descriptors were found most important: bactericidal activity particularly increases with high values of the best volume (BV11(OH2)) and the minimum energy (Emin1(OH2)) of the water probe, high values of the integy moment (ID(DRY)) of the lipophilic probe, and high values of the hydrophilic region (W(O)) of the hydrogen bond acceptor probe. Best volume (BV31(OH2)) of the water probe and best volume (BV12(DRY)) and lipophilic regions (D(DRY)) of the lipophilic probe as well as H-bonding capacity derived with the CO probe (HB(O)) are inversely related to activity. PLS analysis yields a five-component model with an r(2) of 0.83 and a q(2) of 0.43 after variable selection via fractional factorial design (FFD). Chemometric modeling could be improved by including newly derived SHAPE descriptors, which were merged with the VolSurf descriptors and subjected to PLS analysis. The global model of this extended VolSurf approach is optimal with two components and exhibits a significantly improved statistical quality; a marginally reduced r(2) (0.75 versus 0.83) is more than compensated by a highly improved predictivity with a q(2) of 0.63 versus 0.43. To prove model quality, external prediction of seven test set quinolones was performed. The precise prediction of all test set molecules nicely demonstrates the robustness and statistical significance of the obtained chemometric model using the extended VolSurf approach.